1. Field of the Invention
The present invention is directed to a variable gap stop arrangement for a driving unit which, as one example, moves a semiconductor wafer to a desired height within a semiconductor processing chamber.
2. Discussion of the Background
In the processing of semiconductor wafers, the semiconductor wafers are at various times placed inside a process chamber, a deposition chamber, etc. In those chambers the semiconductor wafers are subjected to different processings.
For example, within an etching processing chamber a semiconductor wafer is placed on a semiconductor support element, such as a chuck which also serves as a lower electrode. Positioned above the chuck is an upper electrode. Further, positioned circumferentially around the chuck and the upper electrode is a rotating magnet. The chuck, the upper electrode, and the rotating magnet generate a plasma used to etch the semiconductor wafer placed on the chuck.
In such an etching processing chamber, the semiconductor wafer must be positioned at a certain distance from the upper electrode. To achieve that operation the chuck on which the semiconductor wafer is mounted is moved up and down within the processing chamber by a drive system to a desired height below the upper electrode.
FIG. 1 shows a background drive system to position a chuck at a desired height in a semiconductor processing chamber. FIG. 1 shows a cylinder 10 on which a chuck (not shown) is mounted, and a semiconductor wafer (not shown) is in turn secured on the chuck.
In FIG. 1, three drive screws 12 are provided which when rotated drive the cylinder 10 up and down. Formed around the three drive screws 12 is a drive chain (not shown) to rotate the three drive screws 12, and the drive chain is in turn is driven by a motor (not shown).
With the drive system of FIG. 1 an operator of the semiconductor processing equipment can set a desired height of a semiconductor wafer within a process chamber. Then, the motor drives the drive chain to in turn drive the three drive screws 12, which in turn move the cylinder 10 to a desired height within a semiconductor processing chamber. Further, various sensors and feedback systems can be employed to monitor the height of the chuck within the processing chamber to ensure that the chuck supports the semiconductor wafer at the desired height. Thus, utilizing the drive system for the cylinder 10 supporting a chuck as shown in FIG. 1 allows a semiconductor wafer to be replaced at a variable height within a processing chamber.
However, the chain drive system of FIG. 1 suffers from several drawbacks for semiconductor processing. First, semiconductor processing requires extremely precise operations and also requires a very high level of cleanliness. The chain drive of FIG. 1 has a drawback in that it often generates vibrations within the semiconductor equipment which may be detrimental to the semiconductor equipment. Further, the chain drive may require lubricants which could result in contaminants finding their way into the semiconductor equipment, and any contaminants in semiconductor equipment may result in contaminating a semiconductor wafer being processed.
An alternative system for positioning a semiconductor support element is shown in FIG. 2. FIG. 2 shows a chuck 21 on which a semiconductor wafer is secured. The chuck 21 in turn is supported by a cylinder 22 which moves up and down to pass through an upper support bracket 27 and a lower support bracket 25. The cylinder 22 also includes a lower base 26 attached thereto to move with the cylinder 22. The cylinder 22 may be a pneumatically air driven cylinder which moves upward and downward based on a control of an airflow, in a standard way.
To ensure that the chuck 21 is at an appropriate height within a processing chamber, the lower base 26 includes three stop screws 24. The stop screws 24 may have an adjustable height, as shown by the shadow line in FIG. 2. When the cylinder 22 is moved upward to move a semiconductor wafer secured on the chuck 21 into a processing chamber, the stop screws 24 will abut against a bottom of the lower support bracket 25 to stop the cylinder 22 at an appropriate position, which as a result stops the chuck 21 at an appropriate height within the processing chamber. An operator of semiconductor equipment including the drive system of FIG. 2 may manually adjust the positioning of the stop screws 24 (as shown by the dashed line in the front shown stop screw 24) to adjust the height at which the chuck 21 stops within the processing chamber. With such a device, the movement of the cylinder 22 is only stopped by the stop screws 24 abutting against the lower support bracket 25.
The benefits of the drive system of FIG. 2 with respect to the drive system of FIG. 1 is that the drive system of FIG. 2 does not require a chain drive and thus avoids the vibration and potential contamination of the chain drive system. A drawback with the drive system of FIG. 2 is that it is more difficult and cumbersome for an operator to adjust the height of the cylinder 22 within the processing chamber since performing such an adjustment requires an operator to manually and properly adjust the position of the stop screws 24.
One object of the present invention is to provide a novel drive system, which may find particular application in semiconductor processing equipment, which provides the benefits of allowing a height of an object support to be varied.
A further object of the present invention is to provide a novel drive system, which may find particular application in semiconductor processing equipment, which allows a height of an object support to be easily varied by an operator, and without generating vibration and contaminants.
A further object of the present invention is to provide a novel drive system, which may find particular application in semiconductor processing equipment, which can be implemented in semiconductor processing equipment which utilizes a pneumatic cylinder drive unit for driving a chuck on which a semiconductor wafer is placed.
To achieve the above and other objects, the present invention sets forth a novel variable gap stop device which can stop the movement of a drive unit, such as a pneumatically driven cylinder which moves a chuck on which a semiconductor wafer is secured in a semiconductor processing equipment. In the present invention the drive unit includes at least one positioning surface. A movable gap stop unit includes at least one stop surface, and in a preferred embodiment may include two or more different stop surfaces each at a different height. A cylinder with a rod moves the movable gap stop unit to position at least one of the stop surfaces to be in and out of alignment with the at least one positioning surface of the drive unit.
With such a structure and operation in the present invention, the at least one positioning surface of the drive unit can abut against one of the plural stop surfaces of the movable gap stop unit. Based on which of the plural stop surfaces the positioning surface of the drive unit abuts against, a height that the drive unit moves the positioning surface can be controlled, e.g. the height that the cylinder moves the chuck, and consequently the height of the chuck within a semiconductor processing chamber, can be controlled.
Thereby, the structure in the present invention provides an easily executable control such that an object, such as a semiconductor wafer, can be easily and efficiently positioned at variable heights within a device, such as a processing chamber.